Abstract:
This study investigated the effect of various rates of an organic fertilizer (processed poultry manure) on the growth, yield and nutrient content of cabbage with the objective of recommending organic fertilizer as the sole nutrient source, for organic cultivation of cabbage under shelter in the lowlands.
The experiment was conducted on a clay soil, under a tunnel-shaped structure with plastic roof and netted sides, at the MARDI headquarters in Serdang.
Treatments consisted of varying rates (0, 15, 30, 45 and 60 t/ha) of processed poultry manure.
The control treatment was an inorganic fertilizer (N:P2O5:K2O:MgO = 12:12:17:2) applied at 2 t/ha.
Plot size used was 14 m by 1.5 m.
One month old cabbage seedlings (KK cross) were transplanted on 7th July 2003, on raised beds, at 60 cm x 60 cm triangular planting, to give 46 plants/plot.
Harvesting started at 10 weeks after transplanting, on 16th September 2003 and was completed in one week.
Results obtained showed a quadratic yield response to rates of organic fertiliser, represented by the equation Y = 9.832 + 0.636x – 0.008x2, where Y = yield in t/ha and x = organic fertilser in t/ha.
The optimum rate of fertiliser is 39.75 t/ha.
Yields obtained at this rate was 22.47 t/ha.
A quadratic response to fertilizer rates was also obtained for canopy width.
A linear response was obtained for head diameter.
Organic fertiliser rates had significant effects on P and K contents.
The N content with increasing rates of organic fertiliser was only significant for the outer leaves.
Organic fertiliser rates did not significantly affect Mg content.
Nitrate contents did not differ significantly but were highest with the inorganic fertiliser in the outer leaves.
All rates of organic fertiliser improved soil chemical properties compared to the inorganic fertiliser.
It is concluded that about 40 t/ha of processed poultry manure, as the sole source of nutrients, can be recommended for organic cultivation of lowland cabbage grown on clay soils under shelter.